Because of the difficulty involved in the performance of formal tests of urinary acidification for the diagnosis of distal renal tubular acidosis, "short" tests have been proposed. The goal of this series of studies is to apply findings in animal models of RTA to the diagnosis of these defects in man. A controlled clinical setting will be used to establish if the proposed more convenient tests are reliable for the diagnosis of distal RTA, and to elucidate more fully the pathophysiologic basis of a number of disorders of distal RTA.